This page has moved. Click here to view.
There has been increasing interest in the role of reactive oxygen species (ROS), including free radicals, in the normal process of brain aging and in the pathophysiology of neurodegenerative disorders, such as Alzheimer's disease (AD). A number of patients with AD are also taking antioxidant therapy on the recommendation of their caregivers or physicians in the belief that such therapy may offer some neuroprotective ginkgo biloba, ginko biloba, gingo, Alzheimer's, Alzheimers
An antioxidant is any substance that is able to protect against the damages of oxidative stress caused by reactive oxygen species such as free radicals. Each ROS has a specific antioxidant. As described above, SOD scavenges out the superoxide radical and converts it to the less reactive hydrogen peroxide. Similarly, catalase and glutathione peroxidase seek out hydrogen peroxide and convert it to
| Antioxidant | Function |
|---|---|
| Vitamin E | Protects against lipid peroxidation |
| Selegiline | Prevents the excessive degradation of catecholamines |
| Vitamin C | Blocks the creation of nitrosamines by reducing nitrites |
| Vitamin A | Scavenges the lipoperoxyl radical and thereby interferes with lipid peroxidation |
| Betacarotene | |
| Coenzyme Q | Prevents O2- formation in mitochondria by accepting electrons |
| Glutathione | Converts hydrogen peroxide into water and oxygen |
| Peroxidase | |
| Catalase | |
| Superoxide | Converts the superoxide radical into hydrogen peroxide |
| Dismutase |
In another multicenter randomized trial, the safety and efficacy of a preparation of ginkgo biloba (EGb) was evaluated in a group of AD and vascular dementia subjects. The mechanism of action is not well known, but may involve antioxidant and other mechanisms. In a 1-year study, the effect 40 mg of ginkgo taken three times daily was compared with that of a placebo. There was a relatively high drop-out rate (about 50%), and the analyses of evaluable patients showed a modest benefit for ginkgo biloba compared with placebo on cognition as well as on a caregiver-rated scale evaluating memory, social functioning, and behavior. The subgroup of AD subjects showed modest benefits though the sample size did not permit an analysis of the subgroup of vascular dementia subjects. In all of these analyses, there were no drug placebo differences noted on a global scale rated by the physician. The latter finding, the drop-out rates, and some issues related to design and caregiver ratings are potential weaknesses of the study. This study too has been criticized for the pooling of AD and non-AD cases and other design issues. However, there are other smaller studies that have reported cognitive benefits with varying doses of ginkgo (all greater than 100 mg per day) in dementia. In general, ginkgo is reported to be well tolerated and safe in controlled studies with a profile similar to placebo. Its availability without prescription has made its true efficacy and safety difficult to assess. Thus, one or more multicenter studies are needed to confirm the benefits of ginkgo in AD, determine the optimal dose and duration of therapy, ascertain the safety and efficacy when combined with other AD therapies (such as donepezil), and study the long-term effects on the degenerative process. The low cost and tolerability make ginkgo biloba a highly attractive candidate for further investigation in AD and other dementias ginkgo biloba, ginko biloba, gingo, Alzheimer's, Alzheimers